參數(shù)資料
型號(hào)： LTC1539
廠商： Linear Technology Corporation
元件分類(lèi)： 基準(zhǔn)電壓源/電流源
英文描述： Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators
中文描述： 雙通道高效率，低噪聲，同步降壓型開(kāi)關(guān)穩(wěn)壓器
文件頁(yè)數(shù)： 11/32頁(yè)
文件大?。?/td> 451K
代理商： LTC1539
11
LTC 1538-AUX/LTC 1539
OPERATIO
N
Frequency Synchronization
U
A Phase-Locked Loop (PLL) is available on the LTC1539
to allow the oscillator to be synchronized to an external
source connected to the PLLIN pin. The output of the
phase detector at the PLL LPF pin is also the control input
of the oscillator, which operates over a 0V to 2.4V range
corresponding to –30% to 30% in frequency. When
locked, the PLL aligns the turn-on of the top MOSFET to
the rising edge of the synchronizing signal. When PLLIN
is left open, PLL LPF goes low, forcing the oscillator to
minimum frequency.
Power-On Reset
The POR1 pin is an open drain output which pulls low
when the main regulator output voltage of the LTC1539
first controller is out of regulation. When the output
voltage rises to within 5% of regulation, a timer is started
which releases POR1 after 2
16
(65536) oscillator cycles.
Auxiliary Linear Regulator
The auxiliary linear regulator in the LTC1538-AUX and
LTC1539 controls an external PNP transistor for operation
up to 500mA. A precise internal AUXFB resistive divider is
invoked when the AUXDR pin is above 9.5V to allow
regulated 12V VPP supplies to be easily implemented.
When AUXDR is below 8.5V an external feedback divider
may be used to set other output voltages. Taking the
AUXON pin low shuts down the auxiliary regulator provid-
ing a convenient logic-controlled power supply.
The AUX block can be used as a comparator having its
inverting input tied to the internal 1.19V reference. The
AUXDR pin is used as the output and requires an external
pull-up to a supply of less than 8.5V in order to inhibit the
invoking of the internal resistive divider.
INTV
CC
/EXTV
CC
Power
Power for the top and bottom MOSFET drivers and most
of the other LTC1538-AUX/LTC1539 circuitry is derived
from the INTV
CC
pin. The bottom MOSFET driver supply is
also connected to INTV
CC
. When the EXTV
CC
pin is left
open, an internal 5V low dropout regulator supplies INTV
CC
power. If EXTV
CC
is taken above 4.8V, the 5V regulator is
turned off and an internal switch is turned on to connect
EXTV
CC
to INTV
CC
. This allows the INTV
CC
power to be
derived from a high efficiency external source such as the
output of the regulator itself or a secondary winding, as
described in the Applications Information section.
The 5V/20mA INTV
CC
regulator can be used as a standby
regulator when the two controllers are in shutdown or
when either or both controllers are on. Irrespective of the
signals on the RUN/SS pins, the INTV
CC
pin will follow the
voltage applied to the EXTV
CC
pin when the voltage applied
to the EXTV
CC
pin is taken above 4.8V. The externally
applied voltage is required to be less than the voltage
applied to the V
IN
pin at all times, even when both control-
lers are shut down. This prevents a voltage backfeed
situation from the source applied to the EXTV
CC
pin to the
V
IN
pin. If the EXTV
CC
pin is tied to the first controller’s 5V
output, the nominal INTV
CC
pin voltage will stay in the
guaranteed range of 4.7V to 5.2V.
(Refer to Functional Diagram)
APPLICATIO
S I
FOR
ATIO
U
The basic LTC1539 application circuit is shown in Fig-
ure1. External component selection is driven by the load
requirement and begins with the selection of R
SENSE
. Once
R
SENSE
is known, C
OSC
and L can be chosen. Next, the
power MOSFETs and D1 are selected. Finally, C
IN
and C
OUT
are selected. The circuit shown in Figure 1 can be config-
ured for operation up to an input voltage of 28V (limited by
the external MOSFETs).
W
U
U
R
SENSE
Selection for Output Current
R
SENSE
is chosen based on the required output current.
The LTC1538-AUX/LTC1539 current comparator has a
maximum threshold of 150mV/R
SENSE
and an input com-
mon mode range of SGND to INTV
CC
. The current com-
parator threshold sets the peak of the inductor current,
yielding a maximum average output current I
MAX
equal to
the peak value less half the peak-to-peak ripple current,
I
L
.
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LTC1539CGW 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX
LTC1539CGW#PBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX
LTC1539CGW#TR 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX
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